Apparatus and method for generating high-order harmonic X-ray, and point-diffraction interferometer using high-order harmonic X-ray

Abstract

Disclosed herein is a point-diffraction interferometer which can inspect a surface quality of an optical system for extreme ultraviolet lithography using a high-order harmonic X-ray source with excellent coherence, and an apparatus and method for generating a high-order harmonic X-ray. The present invention uses a high-order harmonic X-ray beam as a coherence light source, thus remarkably reducing the size of an apparatus for generating a light source to approximately 1 / 100 of a device using a light source generated in a conventional synchrotron. Further, the present invention simplifies the construction of an interferometer by employing a thin foil in which a pinhole is formed through a drilling technique using high power femtosecond laser, thus increasing the industrial utility of the interferometer.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates generally to an apparatus and method for generating a high-order harmonic X-ray, and a point-diffraction interferometer using the high-order harmonic X-ray, and more particularly to an apparatus and method for generating a high-order harmonic X-ray source with excellent coherence and realizing a point-diffraction interferometer which can inspect a surface quality of an optical system for extreme ultraviolet lithography using the high-order harmonic X-ray source.[0003]2. Description of the Prior Art[0004]Generally, an interferometer is a device for dividing light emitted from a single light source into two or more light beams in an appropriate manner, overlapping divided light beams to cause the light beams to interfere with one another, and observing an interference pattern of the interfered light beams. An interferometer was mainly used to measure wavelengths, precisely compare lengths or ...

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Benefits of technology

[0010]Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide an apparatus and method for generating a high-order harmonic X-ray, which is a coherent X-ray source, without requiring an additional device to improve coherence.

[0011]Another object of the present invention is to provide a point-diffraction interferometer, which can be greatly simplified in construction and inspect a surface quality of an optical system for extreme ultraviolet lithography using a high-order harmonic X-ray source having excellent coherence and a high power femtosecond laser drilling technique for enabling a micro hole to be formed in a thin foil.

[0014]Further, the present invention provides a high-order harmonic X-ray generating method, the method generating a coherent high-order harmonic X-ray by focusing a high power femtosecond laser beam into a gas-filled hollow tube target, comprising the steps of controlling pressure of the gas and reducing the intensity of long-wavelength harmonics with orders less than a predetermined order using an X-ray filter with low transmissivity in a long wavelength region; reducing the intensity of short-wavelength harmonics with orders greater than the predetermined order by adjusting focused intensity of the high power femtosecond laser beam; and allowing harmonics near the predetermined order to be phase-matched by adjusting the beam size of the high power femtosecond laser.

Problems solved by technology

However, such point-diffraction interferometer is problematic in that the access to a huge synchrotron (with the size of several hundreds of meters) is limited and it is difficult to inspect a great number of optical systems for industrial use.

However, the above point-diffraction interferometer using an X-ray generated in synchrotron is problematic in that additional devices are required to improve the coherence of the light source, thus complicating the entire construction and operation of a measuring device and greatly weakening the intensity of light reaching a sample from a light source.

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